Vaccines are desperately needed in the developing world. Even when they’re available and inexpensive, there’s still a major problem: most vaccines need to be refrigerated. Reaching the relevant populations often means traveling to areas where electricity and refrigeration are spotty at best. Nearly half of the vaccine doses around the world are lost to the heat. Also, the cost of refrigeration contributes to about 80 percent of the cost of the vaccines.

So silk experts at Tufts University have come up with a potential solution: encase the vaccines in silk protein...